Beta-lactoglobulin is the major whey protein in the milk of ruminants and some nonruminants, such us the pig, horse, dog, dolphin, kangaroo, cat and whale. However, milks from humans, rodents, and lagomorphs appears to be devoid of b-lactoglobulin. Although this protein was first isolated 60 year ago, no function has been definitely ascribed to b-lactoglobulin. Recent x-ray crystallographic studies have advanced knowledge of the structure of b-lactoglobulin, which is homologous with that of retinol-binding protein and other proteins, called lipocalycins, the function of which seems to be participation in the transport of small hydrophobic substances.
Furthermore, the ability of b-lactoglobulin to bind retinol, fatty acids, and other hydrophobic substances has also suggested that the biological function of this protein could be the transport of these substances to newborn.